1. Field of the Invention
The Invention relates to fluorescent discharge lamps, and more particularly, to a multi-tube fluorescent discharge lamp which construct multiple glass tubes of different caliber in coaxial structure, both ends of the inner most tube are connected to a cathode respectively isolating, perforating and blocking the discharge path, to form a succession of interconnected discharge chambers, and coating fluorescent material on surface of the discharge tubes. Such an Invention can then have more fluorescent area than a conventional fluorescent lamp of similar size and have higher lumen as well as power conversion efficiency. By comparing with the power consumption of a conventional fluorescent discharge lamp, it is therefore has higher luminous flux.
2. Description of the Prior Art
A conventional fluorescent discharge lamp generally is straight or circular tube type. In order to minimize the size and increase luminosity, straight-shaped tube is bent into a wreath or U type for thin tube. Even in some cases, couples of short straight fluorescent tubes are aligned and connected in parallel, on both ends of the tube, it is connected with a cathode tungsten filament coated with oxide such as Ba, Sr and Ca. In the discharge tube, it is in a state of vacuum and with little Hg and Ar to facilitate the discharge process.
The cross-section of conventional fluorescent lamp tubes is usually a round shape and only one layer of fluorescent material such as phosphor is coated on the surface of the tube inside. When the cathodes on both ends of the tube are triggered by current and high-voltage power is applied electron are released from the two cathodes, causing the tube glows and discharges. The gaseous Ar and Hg molecules are also stimulated to form plasma. Its ions and ultraviolet rays also impact the phosphor. The light is coming from conversion of energy potential.
Because cross-section area of a round tube is larger than that of any shape, the average density of electronic flux inside is lower than in other kinds. Furthermore, the electronic flux on the discharge path is concentrated nearby the axis of the discharge tube, whereas the density of the electronic flux nearby the surface of the discharge tube inside is low.
Therefore, the luminous flux in a round tube can not be enhanced proportionally by increasing the diameter to expand the area of phosphor. Much of energy nearby the axis in the discharge tube will be depleted and converted into heat and the conversion factor of the lumen (Lm) and Watt (W) remains insufficient.
Although there is another kind of lamp with lots of segmented built-in tubes and coated with phosphor to increase the luminous fluorescent area, but it does not form a succession of interconnected discharge path. Therefore, neither a stable discharge path or equable plasma status is not guaranteed, nor an adequate and complete luminescent of fluorescent layers is excited in the discharge tube, because the discharge path takes the shortest distance.
Moreover, due to the narrow spectrum of conventional fluorescent discharge lamp, the color-rendering index (Ra) is low and the color temperature (K) is a bit high causing the illuminated object unable to reveal its colors. In addition, because the cathode on both ends of the conventional fluorescent discharge lamp is hit by electrons, the tungsten filament is then vaporized to become black and it pollutes the fluorescent layer of the tube, luminous efficiency of the fluorescent layer as well as the life cycle of the fluorescent discharge lamp.